Check it out ... the singer leans down and plants a kiss on the model's growing bump as they enjoy a babymoon of sorts in Kyoto. Hailey, dressed in jeans and a black top, beams as her hubby gives her and their unborn little one some sweet attention.

The couple first announced they're expecting with an Instagram post earlier this month -- Hailey flaunted her bump in a lace, white gown while she and JB renewed their vows on a hillside in Hawaii.

As we first told you ... the Rhode Skin founder is 6 months along -- but no word yet on the kiddo's sex.

Since confirming her pregnancy, Hailey has given fans a glimpse into her pregnancy journey -- including her unusual food cravings. So far, HB has been loving pickles topped with egg salad and hot sauce.

While this might be an icky combo for some, Justin's wife can't get enough of it right now ... confirming on her Instagram Stories it's her "biggest craving."

Hailey also happily shared her maternity fashion choices -- showing off her bare bump in crop tops on a number of occasions. She even channeled Mariah Carey at one point, rocking a little butterfly top similar to the one the singer made famous in the early aughts.